The presently disclosed subject matter relates to control of uninterruptible power supplies (UPSs).
An uninterruptible power supply (UPS) is an electrical device that can supply power to a load despite variations in quality and/or availability of utility-based power. One common type of UPS is a double-conversion UPS. A double-conversion UPS receives power from a power source (typically a utility power grid), converts the power from alternating current (AC) to direct current (DC) in a rectifier, and stores at least some of this power in an energy storage device. An inverter changes the DC power from the rectifier and/or the energy storage device into an AC power waveform. The AC power waveform may be supplied to the load.
Because multiple-conversion operation can be relatively inefficient, many UPS devices can operate in an alternative mode to improve efficiency. In one power-saving mode, power to the load may be supplied primarily through a bypass feed path from the utility to the load. In this power-saving mode, power will only be supplied via double-conversion when the utility power supply is disturbed. While such power-saving modes may be more efficient, when disturbances to the utility power supply occur, they could disrupt power to the load. Moreover, decisions as to which mode the UPS should be operated in may be reactive, occurring only after electrical measurements indicate a power supply disturbance has occurred.